Question

Question #c646d

Answer 1

You convert the mass to moles and then multiply by Avogadro's number.

Explanation:

Step 1. Convert the mass to moles

One mole of `"NO"` has a mass of (14.01 + 16.00) g = 30.01 g

∴ `"Moles of NO" =75 color(red)(cancel(color(black)("g NO"))) × "1 mol NO"/(30.01 color(red)(cancel(color(black)("g NO")))) = "2.50 mol NO"`

Step 2. Convert moles to molecules

One mole of a compound contains Avogadro's number (`6.022 × 10^23`) of molecules.

∴ `"Molecules of NO" = 2.50 color(red)(cancel(color(black)("mol NO"))) × (6.022 × 10^23color(white)(l) "molecules NO")/(1 color(red)(cancel(color(black)("mol NO"))))`

`= 1.5 × 10^24 color(white)(l)"molecules NO"`

Your sample contains `1.5 × 10^24 color(white)(l)"molecules of NO"`.